Ubuntu 15.10 is not an LTS (Long Term Support) release, which means that it has a short life support cycle of only 9 months. The OS was officially announced on October 22, 2015, and was dubbed Wily Werewolf by Canonical and Ubuntu founder Mark Shuttleworth.
As all good things must come to an end, since July 28, 2016, Canonical will no longer support the Ubuntu 15.10 operating system, urging those who use it to move to the most recent release. Upcoming security advisories will no longer include info or new package versions for the Wily Werewolf series.
If you’re still using the Ubuntu 15.10 (Wily Werewolf) operating system on your personal computer, please consider upgrading as soon as possible to the newest release of the distribution, Ubuntu 16.04 LTS (Xenial Xerus). Because Canonical will no longer provide security patches and software updates for Ubuntu 15.10, so in time, your PC will become vulnerable.
Submitted by: Arnfried Walbrecht